Definite Laytime: The simplest of the categories, specifies how many days/hours are allowed, whether for loading or for discharging, or for both activities, the latter sometimes being known as for ‘all purposes’. Terms might be: ‘Cargo to be loaded within 5 weather working days of 24 consecutive hours’, or ‘7 working days of 24 consecutive hours, weather permitting, for all purposes’. Calculable Laytime: In these cases periods of definite laytime as described above can only be established once a calculation has first been carried out, based on factors contained in the contract and in the statement of facts form. Calculable laytime can be sub-divided into two further sub-sections: Tonnage Calculations: Tonnage calculations are the most common types of calculable laytime. A contract will state that a vessel is to load and/or discharge at a set rate of tons/tonnes per day/hour. Thus, for a ship loading 40,000 metric tonnes of cargo, minimum/maximum, at a rate of 10,000 tonnes daily, there will be 4 days of laytime available to her charterers. However, it might be that the ship’s Master has a margin within which to load – e.g. 40,000 tonnes/5% more or less. Thus, if the ship eventually loaded 41,258 tonnes of cargo, available laytime can be assessed as follows: 41,258 tonnes ) 10,000 tonnes daily = 4,1258 days. 4,1258 days equates to 4 days 3 hours 1 minute in the following manner Hatch Calculations: Are more complicated than Tonnage Calculations, but occasionally need to be performed: Nonetheless, there are well-established procedures to assist. Let us assume that general cargo vessel ‘HERON’ is discharging bagged wheat flour on the basis of: i) a discharge rate of 175 tonnes per hatch daily, ii) total cargo of 7,000 tonnes, iii)1,575 tonnes cargo in the largest cargo compartment, and iv) vessel has five (5) hatches. ‘Per Hatch daily’: The vessel is to be discharged at 175 tonnes per hatch daily. Thus 5 (hatches) x 175 tonnes = 875 tonnes daily, Thus 7,000 tonnes cargo ) 875 = 8 days permitted laytime.